“Balloons! Balloons!”

The Great and Powerful and Balloon-less Trixie eyed her young charges nervously. “Balloons?” she asked, uncertainly.

One of the fillies, a freckled foal with a bright yellow coat and a fire-red mane, nodded vigorously. “Can’t have a party without balloonth!” She did her best to enunciate - she really did - but the gap where two front teeth were growing in made it impossible not to whistle.

Trixie’s half-quirked grin twitched. Balloons. Darn it! She knew she’d forgotten something. She’d been so puffed-up over the idea of putting on a Special Magic Show that she’d completely forgotten the - apparently - most important part.

Presents, check. Streamers, check. Confetti? Packed safely away in her Great and Powerful Cannon of Magic™. And the cake - that big, beautiful, calorie-packed chocolate cake - was tucked comfortably away in the family’s refrigerator, but that didn’t mean that Trixie’s stomach didn’t growl every time she so much as crossed the door to the kitchen.

Everything was in place. But there were no darned balloons!

Trixie tried to keep the grin on her face. She really did. But the rambunctious jeers and laughter of the foals were starting to get to her. Her eyes latched onto the birthday filly: Snow something, a tiny little thing with a coat so blue it was a wonder she wasn’t shivering.

“Balloons aren’t that important,” Trixie said, her smile twitching, “right?”

Snow considered that for a moment. The room fell silent around her. Then:

“Naw,” she said, shaking her head. She nodded sagely. “Balloons are very important.”

The flock of rowdy foals cheered. A bead of sweat stood out on Trixie’s forehead. Drat!

Balloons - balloons - where was she going to find balloons? It’d been her job to deliver the product, and it was her job to -

A lightbulb went off in Trixie’s head.

“Attention!” she hollered, only somewhat desperately. The crowd fell silent; inwardly, Trixie smirked. They might be foals, but she had more than enough practice bellowing over bawdy crowds. “Fillies and gentlecolts - prepare yourselves to see the biggest balloon Equestria has ever seen?”

The room buzzed with discussion. Quiet, muffled whispers sprung up between the foals. The biggest balloon? The biggest ever?

It took effort to keep her showmare’s cocky grin stapled onto her face, but Trixie managed it - barely. With a deep breath, she puffed out her cheeks, lit her horn, and cast the spell.

And exhaled.

But her belly didn’t deflate.

When a pony breathed in, their tummy expanded - not much, but just enough for their diaphragm to allow more air into their body. Normally, when a pony exhaled, their diaphragm would move back into place, and their stomach would return to its normal volume. But pesky things like biology were no match for unicorn arcana.

Trixie took a deep breath in, and her belly inflated a little bit more. When next she exhaled, and then inhaled, though, her magic stepped in to take over the process. Her breaths sped up, and the light of magic began to shimmer across her figure. Slowly, bit by bit, her stomach began to grow larger.

“She’s gettin’ rounder!” one colt hollered. “Look at ‘er tummy!”

A trio of fillies shrieked. Trixie just grinned and kept on puffing.

Her belly by now was large and round enough to brush up against the insides of her legs. But Trixie Lulamoon was far from finished. She’d promised these foals the largest balloon ever, and if she was one thing, it was a showpony. So she kept the spell running, breathing in, and retaining every drop of magic-fueled air as her belly grew larger and larger.

By the time her big, bloated stomach was pressing against the ground, Trixie couldn’t help but groan from the pressure. Her hide felt so taut. Her belly button trembled, and then popped into an outie. Another colt gasped, but Trixie kept her victorious grin onto her face. She felt so light.

And then, just as her hooves were being pushed off of the floor, she began to rise up.

There was only one place for a balloon to go, after all. And as Trixie continued to inflate, her middle passing the diameter of a beach ball and soon approaching a full eighteen feet in circumference, her rotund body continued to float above the ground. The foals ooed and ahed appreciatively, some stomping their hooves on the ground in approval as Trixie’s well-puffed body floated up, and up, and up.

Another groan made Trixie shudder with fullness. Her belly seemed to creak as more and more air was forced inside of it. She was so big - so full - and yet so light. Upward she went; she was more than halfway to the ceiling by now! Her belly button, long since popped out from her stomach, quivered as gallon after gallon of air was pumped inside of her. Her legs puffed out too, her forelegs rounding out even as her great sphere of a belly swallowed them up. Trixie held her breath, puffing out her cheeks as the spell ran its final course.

With a light thwump, she bounced against the ceiling. And then again.

Cheeks rounded out, Trixie beamed down at her audience of stunned foals. Her belly, now fully seven feet across, reached almost all the way down to the streamer-strewn carpet. She was hugely, gloriously round - and the perfect example of a balloon, she thought smugly.

“Behold!” she bellowed, her voice deepened by her volume. “The Great and Voluminous Trixie!”